Antipump-up tappet



March 3, 1970 J. w. HUMPHREYS 3,493,273

ANTIPUMP-UP TAPPET Filed April 23, 1968 INVENT OR JOHN W. HUMPHREYS ATTORNEYS United States Patent 3,498,273 ANTIPUMP-UP TAPPET John W. Humphreys, Muskegon, Mich., assignor to Johnson Products Inc., Muskegon, Mich., a corporation of Michigan Filed Apr. 23, 1968, Ser. No. 723,463 Int. Cl. F16n 17/06; F011 1/00 U.S. Cl. 123-90 3 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a hydraulic tappet having antipump-up properties. In one of its aspects, it relates to a hydraulic tappet in which pump-up is minimized by the inclusion of a spring within the plunger cavity to bear against the push rod socket.

Hydraulic tappets in internal combustion engines are designed to take up lash caused by changes in the dimensions of the valve train as the engine operates at various conditions. Compensation for this lash is made in a normal hydraulic tappet by a plunger within a tappet body. This plunger rises in the tappet body so as to effectively increase the length of the tappet when Valve train clear ance is present. Modern engines, however, operate at higher speeds, which causes troublesome engine valve spriiig surge to become more pronounced due to the natural harmonics of the spring. When momentary lash caused by valve spring surge is taken up by the hydraulic tappet, during a valve event, the plunger of the tappet does not have suflicient time to return to its normal operating position. The result of this condition is that the intake and exhause valve cannot close at the end of the valve event. This non-closing of the valve results in power loss. The response of the tappet to the valve spring surge is called pump-up. In other words, the plunger pumpsup or creeps-up into a position where the efiective length of the tappet is not proper for permitting the intake or exhaust valves to close.

One solution proposed to this pump-up problem is to drill a hole in the side of the tappet body to vent the high pressure chamber to inlet oil pressure as the piston moves upwardly past a certain point. Although this design is relatively effective to stop pump-up, it is a relatively expensive modification of a conventional hydraulic tappet and makes the tappets very sensitive to initial adjustment.

I have now discovered that valve spring surge in a conventional tappet can be minimized by providing a spring within the tappet plunger which spring bears against the push rod socket, whereby the hydraulic lash will be taken up by momentary separation between the push rod socket and its seat in the plunger.

By various aspects of this invention one or more of the following, or other, objects can be obtained.

It is an object of this invention to provide an improved hydraulic tappet with antipump-up properties.

It is a further object of this invention to provide a simple and inexpensive modification of a conventional tappet to prevent pump-up without affecting its initial adjustment requirements.

Other aspects, objects, and the several advantages of this invention are apparent to one skilled in the art from ice a study of this disclosure, the drawings, and the appended claims.

According to the invention, a spring is provided within a tappet plunger, which spring bears against a push rod socket seated within the plunger. The push rod socket is adapted to engage or contact a push rod as a portion of a valve train. The plunger is axially biased within a tappet body. Fluid intake means are provided in the body and the plunger. A check valve in the bottom of the plunger permits oil to flow out of the plunger through the valve.

The spring within the plunger body is weaker than the biasing means for the plunger so that the push rod socket is normally seated within the plunger. The spring within the plunger body takes up momentary lash within the valve train due to valve spring surge.

The invention will now be described with reference to the accompanying drawing in which is shown a transverse sectional view of a fragmentary portion of an internal combustion engine showing a portion of a push rod and a hydraulic tappet.

Referring now to the drawings, a tappet body 4 is reciprocable within an engine block 2 and is actuated by a cam shaft 6 and a. cam lobe 8. A plunger 10 is reciprocable within tappet body 4 and has a shoulder 19 for seating an apertured plate 18 and a push rod socket 12. A push rod having a passageway 16 bears against the push rod socket 12. At the bottom portion of the plunger 10 a check valve plate 22 is biased by check valve spring 24 against the bottom portion of the cavity 20 formed within the plunger 10. A plunger spring 30 and a valve cage 26 hold the check valve plate 22 and check valve spring 24 in place.

A passage 34 is provided to supply oil to the tappet. The oil passes through passage 36, passage 38, and into cavity 20 within the plunger 10. The oil in cavity 20 can flow through the check valve formed by valve plate 22, and into the pressure chamber 32. The oil in the pressure chamber 32 can then flow under pressure between tappet body 4 and plunger 10 back to passages 36 and 38. Also, the oil in cavity 20 is metered through the holes in aperture plate 18 and flows into passage 40, through hole 42 into passageway 16.

The plunger and push rod socket are limited in the upward movement within tappet body 4 by the retainer ring 44 seated in annular groove 46.

The above described portions of the tappet are of conventional design.

According to the invention, an antipump-up spring 48 is positioned within cavity 20, bearing against the bottom portion of cavity 20 and the bottom of aperture valve plate 18. Spring 48 is not as strong as spring 30 so that normally the push rod socket 12 is seated in the position shown in the drawing.

With the use of spring 48, pump-up at surge speed is avoided due to the fact that the hydraulic lash due to surge is taken up by spring 48. Since cavity 20 is not a high pressure chamber,'the valve spring (not shown) can easily push the spring back to the position shown in the drawing after the valve event and the valve can close.

Under high speed engine operating conditions, a separation occurs in the valve train during the engine valve operating event. Separation usually results from valve spring surge at critical speeds. When separation occurs, spring 48 will force push rod socket 12 upwardly relative to plunger 10 before spring 30 can force plunger 10 upwardly relative to tappet body 4. The faster reaction of spring 48 is due to the freedom of movement of the push rod socket 12 within the plunger 10. The spring 48 is also aided by the engine oil pressure which is present in cavity 20. Movement of the plunger 10 relative to body 4 is opposed by the push rod socket 12 and/or the spring 48. I

Reasonable variation and modification are possible within the scope of the foregoing disclosure and the drawing without departing from the spirit of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a hydraulic tappet having a body, a cylindrical, 10

hollow plunger in said body, means biasing said plunger axially within said body, an annular shoulder within said body, means seated within said plunger for contacting a push rod, fluid intake means in said body and said plunger, check valve means in the bottom of said plunger to permit oil to flow out of said plunger through said valve means, a fluid passage through said contacting means to permit fluid to flow from the interior of said plunger to a push rod seated in said contacting means, a fluid metering plate within said plunger in contact with said push rod contacting means and seated against said annular shoulder for metering fluid in said interior of said plunger to said fluid passage, said fluid metering plate being in contact with said push rod contacting means around the circumference of said fluid metering plate, the improvement which comprises: biasing means within said plunger in forcing relationship to said fluid metering plate and to said contacting means biasing said contacting means and metering plate out of seating engagement with said plunger and to maintain said metering plate in contact with said push rod contacting means at said circumference of said fluid metering plate, thereby preventing pump-up of said tappet during high engine speeds.

2. A hydraulic tappet according to claim 1 wherein said biasing means' within said plunger exerts a lesser force than said means biasing said plunger axially with respect to said body.

3. A hydraulic tappet according to claim 1 wherein said plunger has an internal cavity, said biasing means comprising a spring seated with one end against an end of said cavity and the other end abutting said fluid metering plate, said spring being in compression at least when said contacting means and metering plate is seated within said plunger.

References Cited UNITED STATES PATENTS 3,267,918 8/1966 Ayres. 2,803,231 8/ 1957 Skinner. 2,812,750 11/1957 Lesher. 2,937,632 5/ 1960 Voorhies. 3,142,290 7/ 1964 Lesher. 3,111,119 11/1963 Bergmann.

AL LAWRENCE SMITH, Primary Examiner U.S. Cl. X.R. 

